This invention relates to a sheet feeding device for separating the outermost sheet from a stack of sheets. More specifically, it relates to a sheet feeding device for use in an imaging transport such as a fax, copier or scanner.
Although the sheet feeding art is quite old, modern electrostatic copiers and electronic scanners have required its perfection. The most critical sheet feeding task in a scanner is the document handler. In order to maintain the page sequential order of a stack of original document sheets, the sheets are commonly fed off the bottom of the stack. Because of the weight of the stack, bottom separation is difficult and limits the height of the stack and a top sheet feeder would be desirable.
Document originals often vary in size, weight, age and condition. However, nearly all document handlers presently on the market come with instructions not to feed originals of unusual weight or of poor condition. A feeder which can handle a wide variety of types of originals would also be desirable.
Document feeders for sheet materials typically consist of three basic elements, commonly an urging means such as a roller or belt, a feed means such as a roller or belt, and a retard means or separation device. The urging means imparts a force to the sheet being fed and directs it into the feed means. The feed means transports the sheet to the imaging transport path. The retard means is intended to hold back the other sheets in the stack so that only one sheet is fed into the imaging means at one time.
In a document scanner it is desirable to transport single sheets as described above one-by-one from a stack into the imaging transport. It is also desirable to be able to feed odd documents such as stapled documents, very thin documents, or documents in a protective covering, that would not normally feed well through conventional document feeders that use a retard or separation means. A device that would allow easy conversion between manual feed, where the separation force is removed, and auto feed, would be highly desirable.
In certain situations, it is desirable to disengage or remove the separation means from the paper path for cleaning or replacement. Currently available scanners provide for moving the separation means away from the document by depressing a lever. However, these models use separation rollers that are counter driven and require a drive means associated with the separation means. A device that avoids such rollers would be smaller and more easily serviced.
In one embodiment of the invention, there is provided a sheet feeding device which includes a sheet transport means, a feed means, a separation means, and a clutch means. The device is useful for separating an outermost sheet from a stack. The feed means is for feeding the outermost sheet from the stack and is positioned so as to frictionally contact the outermost sheet to advance the outermost sheet toward the sheet transport means. The separation means is positioned adjacent to the feed means to prevent double feeding along a sheet path between the feed means and the separation means. A nip is defined between the separation means and the feed means. The clutch means is in operable association with the feed means and is for transmitting an intermittent drive force to the feed means. The sheet transport means includes a trailing edge sensing means and a leading edge sensing means. The trailing edge sensing means is for sensing when a trailing edge of the outermost sheet is positioned downstream of the nip and activating the clutch means in response thereto. The leading edge sensing means is for sensing when a leading edge of the outermost sheet is positioned downstream of a first transport roller of the sheet transport means and deactivating the clutch means in response thereto.
In another embodiment of the invention, there is provided a sheet feeding device which comprises a feed means, a separation means, a clutch means, and a retraction means. The sheet feeding device is for separating an outermost sheet from a stack. The feed means is for feeding the outermost sheet. The feed means is positionable in frictional contact with the stack to advance the outermost sheet toward the sheet transport means. The separation means is positioned adjacent to the feed means to prevent double feeding of sheets along a sheet path between the feed means and the separation means. A nip is defined between the feed means and the separation means. The separation means includes an internally braked separation roller. The clutch means is in operable association with the feed means and is for transmitting an intermittent drive force to the feed means. The retraction means is for retracting the separation means away from the sheet path. The retraction means is coupled to the separation means.
In another embodiment of the invention, there is provided a sheet feeding device comprising a stack support means, a feed module, a separation means, a drive means, a clutch means and a sheet transport means. The sheet feeding device is for separating an outermost sheet from a stack. The stack support means is for supporting a stack positioned in a first portion of a housing. The feed module is detachably and pivotally mounted to a second portion of the housing for positioning in contact with the stack. The feed module includes urging means and a feed means. The urging means is mounted in the feed module using an infeed shaft. The feed means is mounted in the feed module using a feed roller shaft. The separation means is detachably mounted to the first portion of the housing by a support means. The separation means is positioned adjacent to the feed means to define a nip between the separation means and the feed means. The drive means is for driving the feed module. The drive means is mounted in the second portion of the housing. The clutch means is connected to the drive means for transmitting an intermittent drive force from the drive means to the feed module. The sheet transport means is mounted to the housing for receiving an outermost sheet from the feed means. The sheet transport means includes a series of transport rollers, a trailing edge sensing means, and a leading edge sensing means. The series of transport rollers is for receiving an outermost sheet from the feed means. The trailing edge sensing means is for detecting a trailing edge of the outermost sheet and is positioned downstream of the nip, so that the clutch means is activated when the trailing edge of the outermost sheet is detected by the trailing edge sensing means. The leading edge sensing means is for detecting a leading edge of the outermost sheet. The leading edge sensing means is positioned downstream of a first transport roller, so that the clutch means is deactivated when the leading edge of the outermost sheet is detected by the leading edge sensing means.
In another embodiment of the invention, there is provided a sheet feeding device which comprises a stack support means, a feed module, a separation means, a sheet transport means, a drive means, a clutch means, and a retraction means. The sheet feeding device is for separating an outermost sheet from a stack. The stack support means is disposed in a first portion of a housing. The feed module is detachably mounted to a second portion of the housing so as to be positionable in contact with the stack. The feed module includes an urging means mounted in the feed module by an infeed shaft; and a feed means mounted in the feed module by a feed roller shaft. The separation means is detachably mounted to the first portion of the housing by a support means and is positionable adjacent to the feed module, so as to define a nip between the feed module and the separation means. The sheet transport means is mounted to the housing and is for receiving an outermost sheet from the feed means. The drive means is mounted to the housing for driving the sheet transport means and the feed module. The clutch means is connected to the drive means and is for transmitting an intermittent drive force from the drive means to the feed module. The retraction means is for retracting the separation means away from the feed module. The retraction means is coupled to the separation means. The separation means comprises an internally braked separation roller.
In another embodiment of the invention, there is provided a method for feeding an outermost sheet from a stack through a sheet feeding device. The method comprises placing a stack on a sheet feeding device; urging an outermost sheet on top of the stack forward using a feed module; separating the outermost sheet from the stack using a separation means; and transporting the outermost sheet through a sheet transport means. The advantage is to control the feed module by an electromechanical clutch driven by a drive means.
It is an object of the present invention to provide a sheet feeding device that is reliable and can be serviced easily by the user. The above described embodiments provide a sheet feeding device that is reliable, inexpensive and easy to service and use with all types of documents. The above described embodiments also provide for retracting the separation means out of the sheet path. This design allows the user to manually feed fragile or stapled documents through the device without any interference with the separation means. The separation means preferably has an internally braked separation roller thus eliminating the requirement of a complex drive system making it easier to remove and clean the internally braked separation roller. The drive means is preferably modular, and is easily removed and serviced. Use of the electronically actuatable clutch permits the sheet to be pulled through the transport rollers with the feed means deactivated. By deactivating the feed means in this manner, the likelihood of paper jams can be reduced.